Pascale Jablonka

Pascale Jablonka is a French/Swiss astrophysicist who specializes in the area of galaxy evolution. She earned a doctorate in astrophysics from the University Paris 7- Denis Diderot in France. She then held a postdoctoral fellowship at the Headquarter of the European Southern Observatory (ESO, Germany), before obtaining a position at CNRS (France). She is currently Directrice de Recherche at CNRS and on leave of absence from Paris Observatory in the Laboratoire d'astrophysique of EPFL. Pascale Jablonka conducts both observations and numerical simulations to gain insights into the formation and evolution of galaxies. Her research focuses on three main topics : > Understanding the nature of the first stars in the Universe > Infering the driving parameters of the galaxy star formation histories > Deciphering the impact of the environment on galaxy evolution. Her research exploits ground-based and space telescopes as well as high performance computing facilities.

GOGREEN: A critical assessment of environmental trends in cosmological hydrodynamical simulations at z approximate to 1

Hung-Hsu Chan, Pascale Jablonka

Recent observations have shown that the environmental quenching of galaxies at z & SIM; 1 is qualitatively different to that in the local Universe. However, the physical origin of these differences has not yet been elucidated. In addition, while low-redshift comparisons between observed environmental trends and the predictions of cosmological hydrodynamical simulations are now routine, there have been relatively few comparisons at higher redshifts to date. Here we confront three state-of-the-art suites of simulations (BAHAMAS+MACSIS, EAGLE+Hydrangea, IllustrisTNG) with state-of-the-art observations of the field and cluster environments from the COSMOS/UltraVISTA and GOGREEN surveys, respectively, at z & SIM; 1 to assess the realism of the simulations and gain insight into the evolution of environmental quenching. We show that while the simulations generally reproduce the stellar content and the stellar mass functions of quiescent and star-forming galaxies in the field, all the simulations struggle to capture the observed quenching of satellites in the cluster environment, in that they are overly efficient at quenching low-mass satellites. Furthermore, two of the suites do not sufficiently quench the highest mass galaxies in clusters, perhaps a result of insufficient feedback from AGN. The origin of the discrepancy at low stellar masses (M-* less than or similar to 10(10) M-circle dot), which is present in all the simulations in spite of large differences in resolution, feedback implementations, and hydrodynamical solvers, is unclear. The next generation of simulations, which will push to significantly higher resolution and also include explicit modelling of the cold interstellar medium, may help us to shed light on the low-mass tension.

OXFORD UNIV PRESS2023

How much metal did the first stars provide to the ultra-faint dwarfs?

Pascale Jablonka, Yves Revaz, Mahsa Sanati

Numerical simulations of dwarf galaxies have so far failed to reproduce the observed metallicity-luminosity relation, down to the regime of ultra-faint dwarfs (UFDs). We address this issue by exploring how the first generations of metal-free stars (Pop III) could help increase the mean metallicity ([Fe/H]) of those small and faint galaxies. We ran zoom-in chemo-dynamical simulations of 19 halos extracted from a Lambda Cold Dark Matter (CDM) cosmological box and followed their evolution down to redshift z=0. Models were validated not only on the basis of galaxy global properties, but also on the detailed investigation of the stellar abundance ratios ([alpha/Fe]). We identified the necessary conditions for the formation of the first stars in mini-halos and derived constraints on the metal ejection schemes. The impact of Pop III stars on the final metallicity of UFDs was evaluated by considering different stellar mass ranges for their initial mass function (IMF), the influence of pair-instability supernovae (PISNe), and their energetic feedback, as well as the metallicity threshold that marks the transition from the first massive stars to the formation of low-mass long-lived stars. The inclusion of Pop III stars with masses below 140 M-circle dot, and a standard IMF slope of -1.3 does increase the global metallicity of UFDs, although these are insufficient to resolve the tension with observations. The PISNe with progenitor masses above 140 M-circle dot do allow the metal content of UFDs to further increase. However, as PISNe are very rare and sometimes absent in the faintest UFDs, they have a limited impact on the global faint end of the metallicity-luminosity relation. Despite a limited number of spectroscopically confirmed members in UFDs, which make the stellar metallicity distribution of some UFDs uncertain, our analysis reveals that this is essentially the metal-rich tail that is missing in the models. The remaining challenges are thus both observational and numerical: (i) to extend high-resolution spectroscopy data samples and confirm the mean metallicity of the faintest UFDs; and (ii) to explain the presence of chemically enriched stars in galaxies with very short star formation histories.

EDP SCIENCES S A2023

How much metal did the first stars provide to the ultra-faint dwarfs?

Pascale Jablonka, Yves Revaz, Mahsa Sanati

EDP SCIENCES S A2023

GOGREEN: A critical assessment of environmental trends in cosmological hydrodynamical simulations at z approximate to 1

How much metal did the first stars provide to the ultra-faint dwarfs?

Stellar metallicity gradients of Local Group dwarf galaxies (Corrigendum) (vol 665, artn A92, 2022)

Stellar metallicity gradients of Local Group dwarf galaxies (Corrigendum) (vol 665, artn A92, 2022)

How much metal did the first stars provide to the ultra-faint dwarfs?

GOGREEN: A critical assessment of environmental trends in cosmological hydrodynamical simulations at z approximate to 1